1. Description of Related Art
The formation of a prescribed thin film on the surface of a substrate is carried out frequently in the production of semiconductor devices such as LSI, display apparatus such as liquid crystal displays and information-recording disks such as hard disks. Film deposition apparatus of this type are furnished with substrate holders of a prescribed construction for holding the substrates in the prescribed position within the film deposition chambers in which film deposition is carried out. The thin film should in fact be deposited only on the substrates, but particles which accumulate to form a thin film are inevitably deposited not only on the surface of the substrate, but also on the surface of the substrate holders. Consequently thin films inevitably accumulate on the surface of the substrate holders as well. The accumulation of a film on the substrate holder surface in this way causes problems such as a loss of processing quality to arise. This is described below using the film deposition apparatus which is used with substrates for information-recording disk purposes as an example.
A plan view which shows the outline construction of a conventional film deposition apparatus for information-recording disk substrates is shown in FIG. 10. The apparatus shown in FIG. 10 comprises a plurality of vacuum chambers 1, 2, 501 which are connected in an airtight manner along a transfer path 80. Furthermore, substrate holders 90 which hold the substrates 9 and a transfer mechanism (which is not shown in the drawing) which moves the substrate holders 90 along the transfer path 80 are provided.
A front outline view which shows the construction of the substrate holder 90 which is shown in FIG. 10 is shown in FIG. 11. The substrate holder 90 includes a plate-like holder body 92 and holding claws 91 which are fined to the holder body 92. The holding claws 91 are arranged in groups of three so as to hold a single substrate 9. Each holding claw 91 comprises a metal plate spring which has been bent into an L-shape. The holder body 92, as shown in FIG. 11, has two circular openings which are slightly larger than the substrates 9. The holder body 92 has roughly L-shaped openings extending from the circular openings and each holding claw 91 is located in such an opening.
The holding claws 91 are fixed to the holder body 92 with screws, and the tips engage with the circumferential edge of the substrate 9. The tips of the holding claws 91 are V-shaped. Thus, the edges of the substrates 9 are dropped onto and enter the V-shaped tips.
Of the three such holding claws 91, the holding claw 91 which is located on the lower side is a movable holding claw. That is to say, there is provided a lever 93 which presses down this holding claw 91 against its elasticity. When mounting the substrate 9 on the substrate holder 90, the holding claw 91 on the bottom side is pressed down by means of the lever 93 and the substrate 9 is located in the circular opening in the middle of the holder body 92. Then, the lever 93 is released and the lower side holding claw 91 is returned to its original state by means of its elasticity. As a result the substrate 9 is engaged by the three holding claws 91, and a state in which two substrates 9 are being held on a single substrate holder 90 is achieved. The same procedure, but in reverse, is used to recover the substrates 9 from the substrate holder 90.
Moreover, as is clear from FIG. 11, the substrates 9 are held on the substrate holder 90 in a vertically mounted state. The surfaces of the substrates 9 which are held on the substrate holder 90 are therefore arranged facing toward the side of the transfer path 80.
One of the plurality of vacuum chambers shown in FIG. 10 is a load-lock chamber 1 in which the substrates 9 are mounted onto the substrate holders 90, and another is an unload-lock chamber 2 in which the substrates 9 are recovered from the substrate holders 90. Furthermore, one of the vacuum chambers 501 is a film deposition chamber in which the prescribed thin film is formed on the surfaces of the substrates 9. Moreover, the other vacuum chambers 501 may be constructed as heating chambers in which the substrates 9 are preheated or they may be constructed as second film deposition chambers in those cases where multilayer films are being deposited.
Moreover, in the apparatus shown in FIG. 10, a return mechanism, not shown in the drawing, which returns the substrate holders 90 from which the substrates 9 have been recovered in the unload-lock chamber 2 to the load-lock chamber 1 is established. Hence, the substrate holders 90 are circulated through the plurality of vacuum chambers 1, 2, 501 and the return mechanism so that they can be used to hold substrates 9 repeatedly.
2. Field of the Invention
The inventions of this application concern film deposition apparatus in which prescribed thin films are deposited on the surface of a substrate, and more precisely it concerns the removal of the films which accumulate on the surfaces of the substrate holders which hold the substrates in apparatus of this type.